net/sched: Add separate check for skip_hw flag

Creating a difference between two possible cases:
1. Not offloading tc rule since the user sets 'skip_hw' flag.
2. Not offloading tc rule since the device doesn't support offloading.

This patch doesn't add any new functionality.

Signed-off-by: Hadar Hen Zion <hadarh@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>